1. Field of the Invention
The present invention relates to a fastener for attaching materials that normally would be fastened with a screw or with a finish nail. In particular, the present invention is directed to a fastener having a self-removing head which will shear off from the shaft of the fastener when rotated in a direction counter to the fastening direction leaving a counter sunk fastener.
2. Prior Art
Finish nails are often utilized in applications where screw heads are not desirable to be seen, such as on fine pieces of furniture. Finish nails are also utilized in applications where it is not desired to utilize a regular nail having a normal head or a normal screw having a normal head which requires counter sinking the hole and covering the nail head or screw head.
Attempts to address these issues in the past include Dungeon (U.S. Pat. No. 3,096,680) which discloses a double-headed nail with wings that project outwardly from the shaft. A flat web 24 may be gripped by a claw hammer and twisted to remove the head, thus providing a break-off head for a nail.
Holmes (U.S. Pat. No. 1,698,951) discloses a threaded screw with spiral grooves 4 extending from the end of the shank to the base.
Capuano (U.S. Pat. No. 4,273,175) discloses a threaded bolt with retainer elements 28 similar to barbs in order to prevent reverse rotation.
Reed (U.S. Pat. No. 4,662,806) discloses a lacing plug 60 with a break-off groove 70.
Padula (U.S. Pat. No. 5,120,168) discloses a threaded screw 4 with a narrow neck 2 connected to a head 1 to permit break off of the head, at a torque equal in the clockwise and counter clockwise direction.
Kesselman (U.S. Pat. No. 5,228,250) discloses a threaded bolt with reduced thickness of metal to shear apart or rupture upon application of torque.
Jeanson et al. (U.S. Pat. No. 5,531,554) discloses a screw fastener with collar 30 having radial notches 31.
Petri (U.S. Pat. No. 5,584,625) discloses a bolt with a shearable head 1 having a taper section 7 forming a predetermined breaking point 6.
Grunbichler (U.S. Pat. No. 5,713,705) discloses a threaded bolt having a torque head 3 which breaks off from a permanent clamping head 2.
Nojikawa (U.S. Pat. No. 5,868,536) discloses threads 4 provided with protrusions at every pitch which protrude from threads 4 in order to prevent loosening of the screw.
Ying-Feng (U.S. Pat. No. 6,062,788) discloses a nail with a nail head 10 which may be rotated to one side so that the nail head is separate from the nail body 11 by virtue of indentations 15.
Koma (U.S. Pat. No. 6,146,070), in FIGS. 14 and 15, discloses a break-off head for a bolt.
Nevertheless, there remains a need to provide a finish screw fastener which will provide the superior holding power of a threaded screw while producing a small diameter hole like that of a finish nail.
There remains a need to provide a finish screw fastener having a self-removing head.
Accordingly, it is a principal object and purpose of the present invention to provide a finish screw fastener that has superior holding power compared to the holding power of a finish nail, spike, staple or pin.
It is a further object and purpose of the present invention to provide a finish screw fastener that permits insertion into materials with common tools, such as a Phillips, flat blade, or hex head screwdriver.
It is a principal object and purpose of the present invention to provide a finish screw fastener having a self-tapping design that does not require creation of a pilot hole to permit initial insertion to avoid splitting of common materials such as wood or plastics.
It is a further object and purpose of the present invention to provide a self-removing head that shears off of the fastener shaft when it is turned in a counter clockwise direction at a point after insertion into the fastened material by turning in a clockwise direction.
It is a further object and purpose of the present invention to provide a finish screw fastener that allows counter sinking into materials after the screw head is removed without having to manually counter sink the screw.
It is a further object and purpose of the present invention to provide a finish screw fastener having a design that will not scratch the surface of the fastened material while the fastener is reaching its final depth prior to removal of the fastener head.
It is a further object and purpose of the present invention to provide a finish screw fastener that can withstand large clockwise torque force in relation to counter clockwise torque force so that the fastener can be used in a wide range of both hard and soft materials.